Lactobacillus plantarum and Lactobacillus pentosus grouped into one protein profile cluster at r greater than or equal to 0.70, separate from Lactobacillus casei, Lactobacillus sake, and Lactobacillus curvatus. Similar sugar fermentation reactions were recorded for representative strains of L. plantarum and L. pentosus. Representative strains, including the type of each species, were selected from the different protein profile clusters and their genetic relatedness determined by using numerical analysis of random amplified polymorphic DNA (RAPD)-PCR, The type strains of L. plantarum (ATCC 14917(T)) and L. pentosus (NCFB 363(T)) displayed different RAPD profiles and grouped into two independent clusters, well separated from L. casei, L. curvatus, and L. sake, Numerical analysis of RAPD-PCR proved a reliable and accurate method to distinguish between strains of L. plantarum and L. pentosus.